The present invention relates to the formation of amorphous ternary nickel-chromium-phosphorus alloys by electrodeposition.
Amorphous metal alloys have been studied extensively in the past two decades and have been found to possess a number of superior chemical and physical properties. Among these are excellent corrosion resistance, desirable magnetic properties, and good wear and abrasion resistance.
Heretofore, such alloys have been prepared by several techniques, the most widely used of which being the rapid quenching of the alloy from its melt. While it is possible to produce a variety of different alloys in thin ribbon or wire form in that manner, the technique has inherent limits in the thickness of the stock it can produce and cannot be used to form irregular shapes. Sputtering and plasma deposition have also been used to produce thin foils. As disclosed by A. K. Hayes in U.S. Pat. No. 4,626,448, the latter technique, in particular, has been capable of producing thin adherent coatings of amorphous alloys on relatively larger, complex shapes. Both these techniques again are limited in terms of the thickness of deposit that can be formed within a reasonable time without the creation of destructive residual stresses. Electroless nickel plating has also been used to produce a small number of nickel-based amorphous alloys. While the technique has the capability of building thicker deposits, it is rather limited in the variety of alloys that it can produce and does not allow variation of composition and properties during the course of deposition.
An electron beam evaporation process has been disclosed by K. Matsubara in U.S. Pat. No. 3,900,585 for coating a solid metal onto a substrate. However, in that activated evaporation process which utilizes a plasma, the substrate must serve as cathode and, therefore, must be conductive and the resulting coatings are not amorphous. Iron can also be coated onto a substrate by a plasma-enhanced deposition method involving iron pentacarbonyl in a radio frequency power-induced glow discharge reactor, but again the resulting coating consists of iron crystallites embedded in an iron oxide matrix (D. M. Wroge and D. W. Hess, "Plasma-enhanced Deposition of Iron/Iron Oxide Films", Report LBL-9879, 1979).
Amorphous secondary and ternary alloys have been prepared by chemical vapor deposition, as disclosed in copending patent application Ser. No. 170,228, filed on Mar. 18, 1988. While many advantages attend the chemical deposition approach, e.g., the possibility of reproducing complex shapes and virtually unlimited thicknesses of deposits, the methods have practical limitations in terms of the type of materials and apparatus required which curtail its usefulness for large scale industrial applications.
Electrodeposition has been used to form coatings of binary amorphous alloys of nickel-phosphorus and nickel-chromium (Gamblin, U.S. Pat. Nos. 4,554,219; Yanagioka, 4,113,248; and Lashmore, 4,461,680). A chromium-nickel alloy has also been deposited electrochemically in a bath containing hypophosphite (Jordan, 3,917,517). However, no ternary nickel-phosphorus-chromium alloy has been obtained in that manner.
Finally, an amorphous quaternary iron-nickel-chromium-phosphorus alloy was electrodeposited by Feng et al. [Metallic Corrosion, Proceedings: Eighth International Congress on Metallic Corrosion, Frankfurt, Germ., 2, 1121-26 (1981)]. Again, no nickel-phosphorus-chromium alloy was produced and the basic problems of that process remain to be solved, i.e., low current efficiency of deposition and high internal stress in the deposited alloy.
In view of the prior art and its limitations, it is an object of this invention to provide a novel technique to produce amorphous ternary nickel-phosphorus-chromium alloys. Another object is to produce these alloys on an industrial scale. A further object is to form the amorphous ternary alloys by electrodeposition and obtain alloy layers of 10 microns and up. A still further object is to provide a technique that can operate at high current densities.
Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.